expansion port (FC) (E_Port)
In general, a port is a logical device interface with the associated protocol. With Fibre Channel( FC), the FC ports have a special designation that expresses the functionality and is identified by an underscore. The ports only differ from the protocol on the interface in terms of the range of functions.
"E" stands for extended or expanded. An E_Port can be used to connect FC switches to each other or to bridge units via an inter- switch link to form a switching fabric.